This invention relates to a flexible supporting sheath for cables, hoses and the like. It has particular utility where cables, hoses, and the like, used for feeding electric power, control signals, gas, water, oil, etc. are gathered in one or more groups, and supported and guided between moving and fixed parts, or between moving parts, in a robot, or other machine or machine tool.
In the conventional machine tool or the like, a flexible supporting sheath for cable or the like comprises a series of inner frames, adjacent frames being connected by surrounding pieces. The sheath encloses, supports and guides a portion of cable having a fixed end and a moving end, allowing the cable to be flexed repeatedly within a specified range of movement. Each of the frames has two grooves of specified width arranged in uniformly spaced relationship, and the surrounding pieces have flanges which fit into the grooves. Each of the inner frames in the sheath has surrounding pieces at both of its ends so as to make one united assembly.
Bellows-type sheaths have also been used to enclose cables and the like connected between relatively movable machine parts. Bundled cables have also been used to make connections between relatively moving parts.
Although the conventional flexible supporting sheath, comprising frames and surrounding pieces, is capable of bending in a plane, and thus adapted for use with a linearly moving body, it is not suitable for use with a robot capable of universal movement.
In the case of universal or three-dimensional movement, bellows or bundled cables have been used. However, with bundled cables, bunching of the cables may result in aesthetic problems in outer appearance, and furthermore the cables may not be adequately protected. With sheaths of the bellows type it is difficult to cut and make connections. Furthermore, with bellows it is not possible to establish a specific minimum radius of curvature, and adequate strength for supporting the cables cannot ordinarily be attained.
In accordance with the present invention, a flexible supporting sheath for cable and the like is formed by connecting hollow links in an articulating chain characterized by interfitted inner spherical concave surfaces and outer spherical convex surfaces. The links allow the sheath to be bent freely in any direction. The links include stop means for limiting the articulation of joined links beyond a specified angle, thereby establishing a minimum bending radius.
In accordance with the invention, it is also possible to increase the minimum radius of curvature, and even to render portions of a sheath unbendable. This can be accomplished by the use of spacer members inserted between adjoining links whereby bending is prohibited, or partial bending is permitted so that the minimum bending radius is enlarged.
With the conventional supporting sheath consisting of alternated grooved frame elements and flanged connecting pieces, and even with a bellows-type sheath, it was impossible to provide a branch in the midportion of the sheath. Branching is often desirable for making electrical or fluid connections in complex robots or machine tools.
In accordance with the invention, one or more of the links in the flexible sheath has at least three openings. Two of these openings connect respectively to adjacent links in the sheath, while a third opening connects to a branch. The branch can consist of a similar articulated sheath, in which case the third opening may have a spherical fitting surface for connection to a first link of the branch.
Another aspect of the invention relates to preventing the intrusion of water and dust into the interior of the flexible sheath. This invention solves the problems of waterproofing and dust-proofing in a flexible supporting sheath by means of annular seals provided at the engaging parts of the concave and convex spherical surfaces, or by belt seals covering the gaps between adjacent links, or by annular seals which are compressed in these gaps, or by projections formed on the concave or convex spherical surfaces which partially eliminate the gaps between the engaging spherical surfaces.
One problem with a flexible sheath in accordance with the invention is that it is not necessarily easy to connect and disconnect a convex spherical surface and a concave spherical surface. This can be done by application of heat to the concave surface to cause it to expand. However a more effective means of connection and disconnection in accordance with the invention is provided by splitting the links into halves. Each of the halves is provided with two longitudinal faying, or closely meeting, surfaces, and at least one pair of the faying surfaces are engaged to each other by snap-in connection.
To enable a flexible cable supporting sheath to follow a large variety of movements and at the same time stabilize the paths of movement of the sheath, it is frequently necessary to provide a flexible sheath which is fixed at one part thereof, flexible in only one direction with a fixed minimum radius of bend at another part thereof and bendable to a fixed minimum radius in arbitrary directions at still another part thereof. Prior flexible sheaths have been unable to meet such requirements.
This invention satisfies these requirements by a construction in which each of the spherical surfaces is provided with one or more radial holes, and a pin is press fit in a hole in one link and loosely fitted in a hole in an adjacent link. The pin may be provided on a spacer which is inserted in a gap between adjacent links. Alternatively, a spacer inserted in the gap between the adjacent links can have tongues extending in the longitudinal direction and engaged with grooves provided in the links to prevent the links from rotating.
Another way to meet the requirements for various motions such as one-dimensional, two-dimensional and three-dimensional motions in accordance with the invention is to provide one of the spherical surfaces of a link with projections while the other is provided with recesses. The projections are engaged with recesses.
By choosing the appropriate configurations for the projections and recesses and, further, by providing the large diameter part of the outside of the concave spherical surface with a stop projecting in the longitudinal direction, it is possible to accommodate one-dimensional, two-dimensional, no-back-bend, three-dimensional and other motions, while increasing the slipping-off load of the links.
The invention has the following objects:
(1) To provide a flexible supporting sheath for cables and the like which can be smoothly bent in any direction, so that it may easily follow the movable parts of robots and other automatic machines.
(2) To accommodate all movements of factory automation equipment designed for unmanned operation in the factory in response to the needs of recent industrial technology, and to make improved utilization of the flexible supporting sheaths for cables and the like.
(3) To provide a closed and dust-proof sheath structure which is resistant to the entry of foreign materials from outside the structure and in which the cables, hose and the like within the sheath are protected in a superior manner.
(4) To conceal the cables, hoses and the like from view and to provide a sheath having an aesthetically pleasing outer appearance.
(5) To provide a flexible supporting sheath having a predetermined minimum bending radius.
(6) To provide a flexible supporting sheath in which internal cables, hoses and the like are stored in a compact form.
(7) To provide a flexible supporting sheath which is light in weight and does not generate sound when used.
(8) To provide a flexible supporting sheath having a minimum number of different component parts so that it can be economically mass-produced.
(9) To provide a flexible supporting sheath in which the links can easily be connected and their assembly can easily be performed, and the length of which can be changed easily by adding or removing links.
(10) To provide for various operating conditions by the choice of thickness, shape, inserting position and the like, of spacers inserted between the links.
(11) To produce a compact installation of the sheath, improve its outer appearance and increases the safety of operation by using spacers between links to restrict the movement of the sheath.
(12) To facilitate adjustment, restrict the movement of, and stabilize the sheath unit while its entire movement is being confirmed, by the insertion or removal of spacers on site.
(13) To make fluid or electrical connections between one stationary or movable part and a plurality of movable parts, or between one movable part and a plurality of stationary or movable parts, while maintaining electrical and fluid conductors in a compact form.
(14) To increase the lateral rigidity of a flexible connection by providing multiple interconnected parallel sheaths.
(15) To accommodate a wide variety of multiple-branch applications by providing links of various shapes such as L-shape, T-shape, Y-shape, cross-shape and others.
(16) To provide additional support for a flexible supporting sheath by utilizing a branched part of the sheath to support part of the sheath by suspending it, for example, from the main body of a machine.
(17) To provide a flexible multiple-link supporting sheath having an improved sealing structure resistant to penetration of cutting coolants, water, oils or the like from the exterior, while maintaining the feature of the flexible sheath that it can be three-dimensionally bent in arbitrary directions.
(18) To make it easy to make connections of a sheath to fixed or movable machine element on site.
(19) To make it possible to remove and replace individual links conveniently in making repairs or adjustments.
(20) To make it easy to make connections of a sheath to fixed or movable machine element on site.
(21) To provide for simpler and more economical manufacture of molded links by utilizing a split link structure, thereby making it easier to eject the link parts from the mold and increasing the useful life of the mold.
(22) To provide for increased slipping-off load in a flexible multiple-link sheath having spherical mating elements, and to make it possible to mold link elements of various different designs economically.
(23) To limit the directions in which the links of a flexible supporting sheath can be articulated by means of insertable pins or specially shaped spacers, thereby insuring stability of the sheath and restricting its path of movement, as required under various operating conditions.
(24) To increase the tensile strength of the sheath by means of inserted pins.
(25) To limit the freedom of movement of articulating links in various ways by means of interengaging pins and slots or grooves so that different sheath characteristics can be achieved by constructing a cable from a series of identical links, or from a series of links some of which are different from the others.